Novel folliculin gene mutation and an elevated serum vascular endothelial growth factor-D level in the context of cystic lung disease

Birt-Hogg-Dubé syndrome (BHD) is a rare autosomal dominant genetic disorder characterized by the development of benign cutaneous neoplasms, renal tumors, and pulmonary cysts. Caused by mutations in the folliculin (FLCN) gene on chromosome 17, the pulmonary manifestations observed in BHD include multiple subpleural cysts that are frequently associated with pneumothorax. Diffuse cystic lung disease is also commonly encountered in lymphangioleiomyomatosis (LAM), either in isolation or in the context of tuberous sclerosis complex (TS). The diagnosis of BHD is confirmed by identifying pathogenic FLCN germline mutations. Modern evidence, however, supports using serum vascular endothelial growth factor-D (VEGF-D) levels in differentiating LAM from other cystic lung diseases, including BHD, with high specificity. This case report describes the unique finding of an elevated VEGF-D serum level (1290 pg/ml) in a patient with cystic lung disease, bilateral pneumothorax and a novel disease-causing mutation (E280X) in the FLCN gene.